Parasitology Lab 3 Flashcards
Schistosoma Adult worm
Schistosoma means split body. Male is the larger flat worm on the outside, holds the female within the gynaecophoric canal of the male - produce enormous amounts of eggs. Live in blood vessels and feed on RBC - male uses oral sucker to eat and ventral sucker held onto the endothelium. Female has smaller suckers, but male predominantly responsible for feeding and holding the female. Female dependent on male to mature, but once mature there is swapping that occurs. Tuberculations on tegument of male S mansoni and S haematobium, however S japonicum is smooth. Adult worm inside humans (definitive host) - release egg, inside is larval stage known as miricidium which infects a snail in freshwater. Snail asexual reproduction (1st intermediate host), release cercariae -> skin penetration (schistosomes). All other trematodes have second intermediate host where metacercariae in animals, humans get infected by eating metacercariae
Schistosoma Life cycle
Humans infected by free-swimming cercariae penetrating skin, develop into larval stage schistosomulae migrates through circulation, through lungs and back out into the circulation, eventually in the portal vein, pair male and female, mature into adult worms, then migrate to final site (mesenteric or vesical plexus), female release eggs (either stool or urine), inside egg miracidia hatch when contact with fresh water. The miracidia infects a snail, inside the snail various stages of development and eventually cercariae released from snail into the water to continue the life cycle
Schistosoma Eggs
Stool: S mansoni 140um lateral spine, S japonicum 85um rudimentary spine, Urine: S haematobium 150um terminal spine - tap the coverslip with pen - this will help the spine turn over. The spine is not used to penetrate tissue, but is useful diagnostic feature. S intercalatum also has a terminal spine, but is more thin, S mekongi 90um is similar to S japonicum with tiny button-like spike. S mansoni female release 300 eggs per day, S japonicum release 3000 eggs per day
Trematodes Life cycle
Egg hatch miracidium in setting of fresh water, miracidium infect snail footpad, snail releases cercariae, mature to metacercariae on animals or plants (2nd intermediate host), and oral ingestion infects humans
Trematodes Adult worm
Bilaterally symmetrical, flat, leaf-like adults. Hermaphroditic (except schistosomes), complex life cycles with asexual stage in gastropod molluscs
Paragonimus westermani Life cycle
Metacercariae present in crustaceans - humans ingest undercooked crabs -> excyst within duodenum of human. Juvenile worm will migrate up through diaphragm and into the lungs. Adults develop in cysts in lung which are excreted in sputum. Eggs are transported up trachea to mouth (will find eggs in saliva) - spat out or swallowed, and pass unharmed through intestinal system and excreted in faeces. Eggs can be found in sputum or faeces (takes 2-3 months to occur). Leave as unembryonated eggs. embryonate in contact with fresh water, miracidia develop inside egg, hatch and infect snails in the water. inside the snail (3-4 months) release of cercariae that become metacercariae (encysted within crustaceans)
Paragonimus westermani Adult worm
1cm, flat leaf-like shape. Oral and ventral sucker, branched gut, genital parts (uterus, ovaries and testes with genital pore where eggs are laid from). Adult life span 5y. Adults live in lung cysts - sometimes only find one, but often may find them in pairs (can mate and exchange sperm if have the opportunity)
Paragonimus westermani Eggs
90um long, granular contents (miracidial not developed yet) typical operculum (lid) found In stool or sputum
Clonorchis sinensis & Opisthorchis viverrini Life cycle
Metacercariae within fish (under fish scales, or in flesh) humans eat undercooked fish and ingest metacercariae. Excyst in duodenum to junior worm, adults travel into biliary tree (up the bile duct - takes 1m after ingestion). Adults live ~30y, each worm produce 4000 eggs/day). Eggs passed in stool as embryonated eggs, snails INGEST miracidia, miracidia develop inside snail to cercariae (unforked tail) - free-swimming encyst in the skin or flesh of fresh water fish as metacercariae ready to be ingested by human.
Clonorchis sinensis & Opisthorchis viverrini Clonorchis adult worm
1.5cm oral and ventral sucker, branched testes. Adult matures in 4 weeks after the ingestion of metacercariae. Adults can live up to 30 years
Clonorchis sinensis & Opisthorchis viverrini Opisthorchis adult
1.5cm oral and ventral suckers, lobular (two round) testes
Clonorchis sinensis & Opisthorchis viverrini Egg
30um not distinguishable from each other. Embryonated egg in stool. Operculum, abopercular knob. Smallest of the helminth eggs
Fasciola hepatica Adult worm
3cm live in bile ducts - tegumental spines rub against the bile duct wall causing fibrosis
Fasciola hepatica Life cycle
Human ingest metacercariae on water plant (cattle and sheep also do this). Excyst within duodenum, travel through intestinal wall, on the outside of the liver, push their way through liver into bile duct. Once in the bile duct are adult worms (3-4 months), eggs excreted into faeces as unembryonated eggs, embryonate in water, miricidia hatch, infect the snails, develop to cercariae, leave snail as free-living cercariae excyst on water plants to metacercariae. Adult lifespan 10-15y
Fasciolopsis buski Adult worm
7cm lays 25,000 eggs/day, lives for 1y. Largest of all the human flukes
